1. Field of the Invention
The present invention relates to radio frequency technology, and more particularly to a frequency-multiplied harmonic suppression method for a RF circuit to suppress frequency-multiplied harmonics.
2. Description of the Related Art
With the application of wireless communication systems in different fields, the communication distance and speed of wireless communication systems have been greatly enhanced. Under this condition, the RF power of the transmitter of the RF communication system must be increased. However, due to nonlinear characteristics of the related semiconductor components and the circuit, increasing the RF power of the transmitter can cause generation of odd order and even order frequency-multiplied harmonics at the output end of the circuit, and the generated frequency-multiplied harmonics will be directly radiated into the air to directly interfere with other communication equipments.
To eliminate the interference of frequency-multiplied harmonics, the most commonly used conventional method is the use of a tin plate to directly isolate the circuit. Under normal application, the use of a tin plate can impart an optimal effect to suppress frequency-multiplied harmonics within the safety range and to reduce their interference with other communication equipments only when the output power is under 14˜16 dBm. If the output power of the RF amplifier circuit surpasses the aforesaid range, an insufficient thickness tin plate will not be able to prevent leakage of the frequency-multiplied harmonics, leaving the original problem unsolved.
For suppressing frequency-multiplied harmonics generated during operation of a RF amplifier circuit of output power in or over the range of 27˜30 dBm, an aluminum die-casting housing having a relatively larger wall thickness and stronger anti-penetration power may be used instead of a tin plate. An aluminum die-casting housing of wall thickness in or over the range of 5˜10 mm can effectively prevent leakage of frequency-multiplied harmonics. However, the use of a thick metal housing increases the weight, material cost, molding cost as well as delivery cost. This solution is not blessed.